Background. Male sex workers (MSWs) are at particularly elevated risk for HIV infection and represent an important bridge population potentiating the HIV/AIDS epidemic in India. Most (~60%) MSWs in Chennai and Mumbai have a steady male or female partner/spouse (Humsafar, 2007; Mimiaga 2010), thus the risk for HIV-infection/transmission is not only to/from their sex work clients but also to/from their primary partners. Our team's experience with the population suggests that MSWs are networked with each other and with their clients through the use of mobile phones. Overview of project. This proposal is to develop and pilot test a new intervention that will use mobile phone technologies to reduce sexual risk taking in MSWs in Chennai and Mumbai. Following initial formative work, we anticipate that the intervention will incorporate standard of care HIV and STI testing (during in person assessments) with behavioral risk reduction counseling approaches using problem-solving/motivational interviewing, as well as text messaging of motivational reminders and for risk reduction cues delivered by study staff via participant's mobile phones. Phase 1: The first six months will be an intervention development and refinement phase. We will first conduct qualitative interviews (N = ~20 at both the Chennai and Mumbai study sites) and focus groups to inform the content of the intervention. We will then conduct an open pilot of the intervention with up to 10 MSWs (5 per study site) and assess initial feasibility and acceptability. We will then revise the intervention based on these data and work out any remaining methodological or intervention-development details. Phase 2: The next 18 months will be a RCT pilot of the intervention. One hundred (80 completers: 40 per study site) MSWs at risk for transmitting or acquiring HIV will be randomized to either 1) the mobile phone delivered counseling intervention and standard of care HIV/STI counseling and testing or 2) the control condition-standard of care HIV/STI counseling and testing alone. To maximize generalizability and feasibility, we will include both HIV-infected and HIV-uninfected participants. Accordingly, following the U.S.-India Bilateral Collaborative Research Partnerships on the Prevention of HIV/AIDS and Co-morbidities (R21) mechanism, one of the goals of the project will be to determine whether the structure and content of an intervention can be similar across two heavily populated cities in India. Innovation. To our knowledge, despite the rapid increase in mobile phone usage globally, no study has been conducted using counselors to deliver an HIV prevention intervention via mobile phone technologies in India among MSWs. This will be the first study to assess the acceptability and feasibility of using this technology, with a largely underserved, marginalized, and at risk subpopulation who are already networked through mobile phones. Environment. This proposal grew from ongoing work between Fenway Health, a non-profit community health center and research institute specializing in sexual minority health including HIV/AIDS care and research in Boston, the Tuberculosis Research Centre/ICMR in Chennai, and Gaurav/Humsafar Trust, the largest NGO providing care for sexual minorities, as well as MSWs, in Mumbai.